Contributed by Adriana Piña, GSA Graduate Student Research Grant Recipient

As Isla Tortuga is a relatively young volcano in the central Gulf of California, Mexico, one might expect it to be frequently visited by geologists. However, after Rodey Batiza’s expeditions in the 1970s, to our knowledge no other geologists have set foot on the island for research purposes. Access is not trivial. While Isla Tortuga is a fascinating locality with a well-preserved record of volcanism that can be used to study some of the most recent activity in the Gulf of California, it is also the home for the Crotalus atrox tortugensis, an endemic rattlesnake that inhabits the island. With no natural predators, this rattlesnake is one of the most abundant reptiles on the island. Due to seasonal wind conditions, the best time to visit the island is in the summer, aboard a small fishing boat called a “panga.” Summertime is also when the island reaches its peak temperatures and humidity levels. The combination of the high rattlesnake density and extreme weather conditions renders the island as a hazardous place to conduct field work. 

Main crater of Isla Tortuga with a lava lake in the center of the crater. The lava lake resulted from the last eruption of this volcano.

Isla Tortuga is both the largest and the only subaerial volcano in the Guaymas Basin (Gulf of California), which is a pull-apart basin that exhibits modern seafloor spreading. The International Ocean Discovery Program (IODP) Expedition 385 drilled approximately four kilometers of core in total across eight different sites in the Guaymas Basin. Expedition scientists discovered sills intruding the Quaternary biogenic and terrigenous sediments in the recovered cores. These sills have similar petrographic characteristics to the volcanic units on Isla Tortuga indicating that the island and the sills in the Guaymas Basin may be connected in the subsurface via a magmatic plumbing system.

Thin section of the youngest eruption in Isla Tortuga sampled from the lava lake in the central crater. The photomicrographs above were taken in plane non-polarized light (left) and cross-polarized light (right). The long, white tabular crystals correspond to plagioclases, and the red, yellow, and orange small crystals correspond to pyroxenes.

To understand the relation between Isla Tortuga Volcano and the sills in the Guaymas Basin, I use different petrological techniques that establish a correlation between both study objects. These include petrographic characterization, whole-rock geochemistry, and trace element analyses. Petrographic inspections reveal mineral contents and textures in the rocks, and can be compared for establishment of a preliminary correlation. The whole-rock geochemical analyses help constrain composition of the magmatic source of the lava flows in Isla Tortuga and the sills in the Guaymas Basin. In contrast with the major elements, trace element contents of the lava flows and the sills are nearly identical and provide information about the tectonic environment of magmatic source. A geochronological analysis of the ground mass using the Ar-Ar radiometric method will help to constrain the ages of lavas sampled from Isla Tortuga and corroborate sedimentation events in the Guaymas Basin that were stablish with biogeochemistry geochronology. 

View of one of the cliffs in Isla Tortuga showing the volcanic record capturing several eruption episodes.

While Isla Tortuga is one of the best places to study recent volcanism in the Gulf of California, visiting this Island is costly due to its remote location, and the analyses to answer the our research questions are expensive. The research grants that I received from the Geological Society of America in 2023 and 2024 helped to cover the analytical work for this project. As part of the 2024 award, I worked with three Caltech undergraduate students, each of whom are part of historically excluded and marginalized groups. My mentees, Adoniya Paul, Anna Piland, and Lila Rodriguez-Aceves, worked with me for five weeks last summer preparing samples for LA-ICP-MS analysis and integrating the results of the trace element geochemistry with the whole rock geochemistry and petrography. 

In addition to the support from the GSA Graduate Research Grant program, receiving these awards transformed my confidence as a scientist. It fueled my career growth by enhancing my ability to communicate science, expanding my network, and fostering resilience during fieldwork expeditions. As a Ph.D. student, one of my career goals is to become a scientist. One of my objectives is to build a lab that prioritizes inclusivity, safety, and diversity. I plan to continue encouraging students who are part of marginalized groups to keep pursuing their academic and scientific goals.

The author on the top of Isla Tortuga volcano wearing snake gaiters for protection. Photo credits: Brian Hausback.

About the Author

Adriana is a fourth-year graduate student in geology at Caltech under the supervision of Dr. Joann Stock.  Adriana was awarded with two GSA Graduate Student Research Grants in 2023 from the Continental Scientific Drilling Division as well as a regular graduate research grant. In 2024 she received two more research grants for the project titled “Volcanic history of the Isla Tortuga and its implication with the geological history of the Guaymas Basin, Gulf of California, Mexico.” She received the Lipman Research Award & Harold T. Stearns Fellowship Award. She is a first-generation student, born to a low-income family in Sonora, Mexico. Her complex background has provided her with resilience to face challenges during scientific labor and fuels her to keep promoting inclusivity and diversity in the geosciences.